Die architecture accommodating high-speed semiconductor devices

ABSTRACT

In a semiconductor memory device, a die architecture is provided that arranges memory arrays into a long, narrow configuration. Bond pads may then be placed along a long side of a correspondingly shaped die. As a result, this architecture is compatible with short lead frame “fingers” for use with wide data busses as part of high speed, multiple band memory integrated circuits.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.09/439,972, filed Nov. 12, 1999 issued as U.S. Pat. No. 6,144,675; whichis a continuation of U.S. application Ser. No. 09/301,643, filed Apr.28, 1999 and issued as U.S. Pat. No. 5,995,402; which is a continuationof U.S. application Ser. No. 09/023,254, filed Feb. 13, 1998, and issuedas U.S. Pat. No. 5,936,877.

TECHNICAL FIELD

This invention relates generally to semiconductor devices. Inparticular, this invention relates to die architecture for semiconductormemory devices configured to execute high speed applications, such asthose performed in synchronous dynamic random access memory devices.

BACKGROUND OF THE INVENTION

Assembling an integrated circuit package often involves attaching a dieto a lead frame. As an additional part of assembly, bond wires are usedto electrically connect the conductive leads of the lead frame to thedie's bond pads. The die/lead frame assembly is then encased in ahousing with the outer ends of the conductive leads remaining exposed inorder to allow electrical communication with external circuitry. Thedie's architecture may represent one of many circuitry configurations,such as a Dynamic Random Access Memory (DRAM) circuit or, morespecifically, a synchronous DRAM (SDRAM) circuit.

The high speed synchronous operations associated with SDRAM circuitryoften involve communication with an external device such as a data bus.Occasionally, the data bus may be relatively wide in comparison to thestandard width of prior art SDRAM dies. The width of the data bus, inturn, requires an appropriate number of conductive leads positioned toaccommodate the bus. Further, the position of the conductive leads andtheir spacing limitations require a certain amount of die space for bondpad connection. However, the prior art does not provide a die having oneparticular region that can provide enough bond pads to accommodate allof the conductive leads. Rather, the architecture of the die as found inprior art allows for bond pads to be located in different areas of thedie. Consequently, conductive leads of different lengths are needed toconnect the bond pads to the relatively wide data bus. These differinglengths slow the operations of the SDRAM, or any semiconductor devicefor that matter, as it takes longer for signals to travel through thelonger conductive leads. Thus, if synchronized signals are desired, thespeed of the device is limited by the speed of signal propagationthrough the longest conductive lead. The longer leads also have agreater inductance associated with them, thereby further slowing signalpropagation. Moreover, the inductance in the longer conductive leads isdifferent from the inductance associated with the relatively shortconductive leads. This imbalance in induction makes synchronizing thesignals even more difficult.

Thus, it would benefit the art to have a die configuration that providesbond pads in a common location such that all of the conductive leads ofthe lead frame could be the same length. It would further benefit theart if the die configuration allowed uniformly short conductive leads.Indeed, this desire is mentioned in U.S. Pat. No. 5,408,129, byFarmwald, et al., which discloses a high-speed bus as well as memorydevices that are adapted to use the bus. Specifically, Farmwald '129discloses a narrow multiplexed bus, as demonstrated by Farmwald'spreferred embodiment, wherein the bus comprises only nine bus lines.Accordingly, Farmwald's narrow bus allows for a relatively low number ofbond pads on the die of a memory device. Farmwald '129 concludes that itwould be preferable to place the small number of bond pads on one edgeof each die, as that would allow for short conductive leads. Farmwald'129 at col. 18, ln. 37-43. However, it is possible to do so underFarmwald '129 only because the “pin count . . . can be kept quite small”due to the narrow architecture of the bus. Id. at ln. 17-18.

Contrary to the teachings in Farmwald '129, it would be advantageous attimes to accommodate a relatively wide bus requiring a large number ofpins. It would therefore be additionally advantageous to provide a diecapable of providing the correspondingly large number of bond pads onone side of the die.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides die architectures allowingfor the relocation of the die's bond pads. One embodiment of thisinvention arranges for all of the die's bond pads to be located on oneside of the die, with the corresponding memory banks arrangedaccordingly. In a preferred embodiment, the length of the die sidehaving the bond pads is extended relative to prior architectures and thememory arrays are shaped to follow along the extended side.Consequently, the perpendicular sides contiguous to the extended sidemay be shortened. This architecture has the advantage of allowing thedie to cooperate with a lead frame having conductive leads of the samelength, thereby balancing inductance and aiding in the ability tosynchronize signals. This architecture also has the advantage ofallowing the conductive leads to be relatively short, which furtherincreases the operational speed of the die's circuitry and decreasesinductance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the architecture of a SDRAM chip as found in the priorart.

FIG. 2 illustrates an SDRAM chip within a lead frame as found in theprior art.

FIGS. 3a and 3 b portray a first exemplary embodiment of the presentinvention.

FIG. 4 represents an embodiment of the present invention in cooperationwith a lead frame.

FIGS. 5a and 5 b demonstrate a second exemplary embodiment of thepresent invention.

FIGS. 5c and 5 d illustrate a third exemplary embodiment of the presentinvention.

FIGS. 6a and 6 b depict a fourth exemplary embodiment of the presentinvention.

FIGS. 6c and 6 d depict a fifth exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 depicts the architecture of an SDRAM 20 as it exists in the priorart. The SDRAM 20 is fabricated on a die 22 and includes sixteen memorybanks B0 through B15. The shape of each bank is determined by the numberand arrangement of component sub-arrays. In this prior art example, eachbank comprises a row of sixteen sub-arrays. Bank B0, for example,comprises sub-arrays 000 through 015. Similarly, bank B1 comprisessub-arrays 100 through 115. For purposes of explaining the currentinvention, it is understood that each bank is analogously numbered,ending with sub-arrays 1500 through 1515 comprising memory bank B15.Each sub-array contains a number of memory bit components andaccompanying n/p channel sense amplifier circuitry 26 as well as rowdecoder circuitry 28. The banks B0-B15 are also serviced by a first64×DC sense amp 30 and a second 64×DC sense amp 32. It should be notedthat the size and number of DC sense amps can vary based on thecompression rate desired. Column decoder circuitry 34 is located next tothe DC sense amps 30 and 32; and a column select line 36 extends fromthe column decoder circuitry 34 through all of the memory banks B0-B15.Logic circuitry is located in a region 38 on the other side of the DCsense amps 30 and 32 relative to the memory banks B0-B15. Bond pads 40are placed on the perimeter of the die 22 to allow easy access. Forpurposes of this application, the term “bond pad” includes anyconductive surface configured to permit temporary or permanentelectrical communication with a circuit or node. Further, it should benoted that there exists a series of bond pads—defined here as accesspads, wherein each access pad of the series is coupled to one sub-arrayof each bank, thereby allowing electrical signals to access thosesub-arrays. For example, access pad 40A is defined to be coupled tosub-arrays 000, 100, 200, 300, 400, through 1500. Access pad 40G iscoupled to sub-arrays 006 through 1506. Access pad 40P, in turn, isdefined to be coupled to sub-arrays 015 through 1515. Accordingly, thereare thirteen other access pads, each associated with a correspondingcolumn comprising one sub-array from every bank. In order to keepconnective circuitry to a minimum, these sixteen access pads are locatednear their respective sub-arrays. It should be noted that, in FIG. 1,the group of sub-arrays 000 through 1500 is highlighted in bold forpurposes of indicating the common association those sub-arrays have witha particular access pad (such as 40A, for these sub-arrays). Groups006-1506 and 015-1515 are similarly highlighted. Other bond pads 40,representing additional input and output terminals for communicatingwith the die 22, are placed in the remaining available spaces on the die22, which may include more than one side of the die 22.

Packaging of the die 22 may be influenced by the fact that the internalcircuitry of the die 22 will be interacting with a data bus.Specifically, as seen in FIG. 2, the die 22 can be placed within a leadframe wherein the conductive leads 48, 50 extend from the die 22 andeventually orient in one direction in anticipation of connecting to thedata bus. In FIG. 2, bond pads 40 that are on the die's near side 42—theside that will be closest to the external device—require only relativelyshort conductive leads 48. However, bond pads 40 along the sides 44, 46contiguous to the near side 42 require longer conductive leads 50.Assuming that the signal propagation rate through the conductive leads48, 50 is generally the same, the longer conductive leads 50 will take alonger time to transmit any signals. Moreover, inductance of the longerconductive leads 50 will be greater than inductance of the shorterconductive leads 48.

FIGS. 3a and 3 b illustrate one embodiment of the current invention thatsolves these problems. In this embodiment, the memory banks areseparated into discontiguous portions. Despite placing portions of thebanks in separate locations, the columnar arrangement of sub-arrays, onefrom each bank, is retained, and the columns are rotated ninety degreesrelative to the configuration addressed above. Thus, rather than beingparallel to the contiguous sides 44 and 46, the columns are now parallelto the near side 42. For example, the sixteen sub-arrays associated withaccess pad 40A (000 through 1500) extended along contiguous side 44 inthe prior art die depicted in FIG. 1. Again, this group of sub-arrayscommonly coupled to access pad 40A is highlighted to show the neworientation of the sub-arrays and of the group in general. In FIG. 3a,this group of sub-arrays now extends along the near side 42. While thisgroup of sub-arrays 000 through 1500 is still relatively near contiguousside 44, this is not necessary for purposes of the current invention;this group could occupy any of the columnar positions depicted in FIG.2. Regardless of the particular position of the columns, it is preferredthat their respective access pad remain relatively close by. Moreover,given this new configuration, each sub-array is now orientedperpendicular to the near side 42 of the die 22.

Further, it should be noted that, while the arrangements of sub-arraysin FIG. 2 might be described as “rows” given the ninety degree rotation,the arrangements are referred to as “columns” or “columnar positions”for purposes of demonstrating the continuity with portions of the diearchitecture in FIG. 1.

As an example of this continuity, the row decoder circuitry 28 andcolumn decoder circuitry are also rotated ninety degrees and, therefore,retain their orientation relative to each sub-array. Column decoderdevices in this embodiment include a first modified column decodercircuit 60 interposed between a 700 series of sub-arrays (700 to 703)and an 800 series of sub-arrays (800-803). In addition, a first modifiedcolumn select line 62 extends from the first modified column decodercircuit 60 through sub-arrays 700 to 000. Similarly, a second modifiedcolumn select line 64 extends from the first modified column decodercircuit 60 through sub-arrays 800 to 1500. This embodiment also includesthree other similarly configured modified column decoder circuits 66,61, and 67, each with their own modified column select lines 68 and 70,63 and 65, and 69 and 71, respectively.

Moreover, instead of two 64×DC sense amps 30 and 32, this embodiment ofthe present invention uses four 32×DC sense amps 52, 54, 56, and 58.However, as in the prior art, the size and number of DC sense ampsmerely affect data compression and no one DC sense amp configuration isrequired for any embodiment of the current invention.

In this exemplary embodiment, the columns are further arranged in groupsof four. In doing so, this embodiment partially retains some of the bankcontinuity found in the prior art. For example, the sub-array sequence000, 001, 002, and 003 of Bank 0 remain contiguous. The Bank 0 sequencecontinues in the next four rotated columns with sub-arrays 004, 005,006, and 007 remaining next to each other. These intervals of bankcontinuity apply to the other memory banks as well and aid in minimizingthe complexity of row decoder and column decoder circuitry. Arrangingthe columns in groups of four also means that certain columns will befurther away from the near side 42 than other columns. As a result,there may be unassociated sub-arrays between a column and its accesspad. For example, connective circuitry (not shown) coupling column003-1503 to access pad 40D will probably pass by sub-arrays withincolumns 002-1502, 001-1501, and 000-1500.

Additionally, this arrangement of rotated columns allows for alteringthe dimensions of the die 22. Not only can the near side 42 be extendedto a length commensurate with the data bus, but the contiguous sides 44and 46 may also be shortened. Moreover, extending the near side 42provides chip space for the bond pads 40 that had been along thecontiguous sides 44, 46 in the prior architecture. FIG. 4 demonstratesthe result of this architecture: when the die 22 is attached to a leadframe 76 having conductive leads on only one side, the die's formationaccommodates short conductive leads 78 of uniform length. Packaging thedie 22 with this lead frame 76, in turn, allows for fast operation ofthe die 22 in conjunction with a device having a relatively large numberof data terminals, such as a wide data bus.

Other embodiments of the present invention can lead to the samepackaging advantages. The exemplary embodiment in FIGS. 5a and 5 b, forinstance, demonstrates that, although the sub-arrays are rotated ninetydegrees as in FIGS. 3a and 3 b, it is not necessary to retain thecolumnar arrangement of the previous embodiment. Instead of the 16×1columns, the sub-arrays in FIGS. 5a and 5 b have been grouped into 4×4associations. As demonstrated in the previous embodiment, there is arepetition of the sub-array pattern at continuous intervals. In theembodiment shown in FIGS. 5a and 5 b, sequential sub-arrays of aparticular bank are separated by sub-arrays of other banks. Sub-arrays000 and 001 of Bank 0, for example, are separated by sub-arrays 400,800, and 1200. As further demonstrated in the previous embodiment, it isstill preferred to configure the access pads near their respectivegrouping. Nevertheless, because the associated sub-arrays in FIGS. 3aand 3 b extend along one dimension and include one sub-array from everybank, there is more sharing of row decoder circuitry 28 as well ascolumn select circuitry 62, 64, 68, 70, 63, 65, 69, and 71 in thatembodiment than in the more fragmented sub-array groupings depicted inFIGS. 5a and 5 b. Accordingly, the embodiment in FIGS. 3a and 3 b is themore preferred embodiment of the two. FIGS. 5c and 5 d represent analternate configuration of 4×4 associations.

There are also alternative embodiments that do not involve rotating theorientation of the sub-arrays, as demonstrated in FIGS. 6a and 6 b.Whereas there are sixteen rows of sub-arrays extending back from thenear side 42 of the die 22 in FIG. 1, the die 22 in FIGS. 6a and 6 b hasa memory configuration only eight sub-arrays “deep.” Further, thesub-arrays are gathered into 8×2 groupings, again with one sub-arrayfrom every bank in each group and with each group associated with aparticular access pad. Moreover, each group is oriented perpendicular tothe near side 42 of die 22. Group 90 has been defined to containsub-arrays 000 through 1500, group 92 contains sub-arrays 001 through1501, and group 94 contains sub-arrays 002 through 1502. While noparticular order of groups is required, it is noteworthy in thisembodiment that the sub-arrays 800 through 1500 in group 90 are next tosub-arrays 801 through 1501 in group 92. In effect, groups 90 and 92could be considered “mirror images” of each other. This mirror imageconfiguration is useful in compressing data for test modes and inmaximizing the opportunity to share row decoder circuitry 28. It canfurther be seen in FIGS. 6a and 6 b that group 94 is a mirror image ofgroup 92, wherein sub-arrays 002 through 702 are respectively contiguousto sub-arrays 001 through 701. While these mirror image configurationsare preferable in a die architecture having 8×2 sub-array groupings,they are not necessary to realize the current invention. As in otherembodiments, this one has a die shape capable of including bond pads ina configuration accommodatable to communication with an external device,with a memory arrangement generally conforming to the die shape.

The embodiment in FIGS. 6a and 6 b also benefits from four 32×DC senseamps 80, 81, 82, and 83. Further, there are two column decoder circuits84 and 85, each associated with respective column select lines 86 and87. Unlike the previous embodiments, however, each sub-array is orientedparallel to the near side 42 of the die 22. FIGS. 6c and 6 d representan alternate configuration of 8×2 associations or groupings ofsub-arrays.

One of ordinary skill can appreciate that, although specific embodimentsof this invention have been described for purposes of illustration,various modifications can be made without departing from the spirit andscope of the invention. For example, embodiments of die architecturecovered by this invention need not be restricted to placing bond pads ononly one side of a die. It may be desirable in certain applications touse a lead frame having conductive leads facing two or more sides of adie. Die architectures included within the scope of this invention couldlocate the die's bond pads to allow for conductive leads of a uniformlength and, more specifically, a uniformly short length on all relevantsides. In addition, the dimensions of the memory banks could be adaptedto conform to a particular die's requirements. If, for example, thenumber of bond pads and the conductive lead pitch limitations require adie side even longer than the near side 42 in FIGS. 5a and 5 b , the 4×4banks of rotated sub-arrays can be replaced with an embodiment having aseries of rotated sub-arrays grouped into 2×8 banks. Accordingly, theinvention is not limited except as stated in the claims.

What is claimed is:
 1. A method of arranging at least one memory bank ona die that also includes contact pads, comprising: dividing a firstmemory bank into at least two portions; and positioning each portion ofsaid first memory bank in an area of said die that is distal from otherportions of said first memory bank, wherein said area is to at most oneside of all contact pads of said die.
 2. The method in claim 1, furthercomprising: dividing a second memory bank into at least two portions;and positioning each portion of said second memory bank in an area ofsaid die that is next to a portion of said first memory bank.
 3. Themethod in claim 2, wherein said step of positioning each portion of saidsecond memory bank comprises positioning a portion of said second memorybank between two portions of said first memory bank.
 4. The method inclaim 3, wherein said step of positioning each portion of said secondmemory bank comprises positioning each portion of said second memorybank in an area of said die that is distal from other portions of saidsecond memory bank.
 5. The method in claim 4, wherein said step ofdividing a first memory bank comprises dividing said first memory bankinto equally sized portions.
 6. The method in claim 5, wherein said stepof dividing a second memory bank comprises dividing said second memorybank into at least two portions equal in size with said portions of saidfirst memory bank.